Flasher bulb for use in ornamental light strings are well known. One known form of flasher bulb, for example, is shown in FIG. 1. This bulb includes an insulating body A which fixes respective nickel wires N1 N2 in position inside a glass shell D. Between the two nickel wires is bimetallic element B, and a tungsten wire C is connected at one end to nickel wire N1 and at its other end to the top of the bimetallic element B thus forming a loop, while the top of the second nickel wire N2 is in contact with the bimetallic element.
When current is passed through the bulb, the bimetallic element B is in a "on" state and all of the bulbs in the string will switch on. After the current has been transmitted for a certain period of time, the bimetallic piece B will deform and separate from the second nickel wire thereby interrupting the current in all the bulbs in the string which are thereby extinguished. Thereafter, the bimetallic element cools and resorts to is original contact condition thereby allowing current to flow and relight all the bulbs. Repeated heating and cooling of the bimetallic strip thereby effects continuous flashing of all the bulbs in a string. Thus, all of the bulbs are lighted and extinguished simultaneously.
A further known form of a flasher bulb, is shown in FIG. 2. In this arrangement, nickel wires N1' and N2' are fixed in position on an insulating element A' inside a glass shell D' and a bimetallic element B' is bent in the shape of an arc and connected with tungsten wire C' at the top while the outside of the bimetallic element is connected by spot welding to the second nickel wire N2 and the tungsten wire is itself connected to the first nickel wire N1'. When current is caused to flow through the bulb, the tungsten wire will brighten and produce heat, and the bimetallic element thus heated will bend causing its lower end to move towards the first nickel wire N1'. When the bimetallic element contacts the first nickel wire current flow to the tungsten wire will be obstructed and the bulb will be extinguished. However, current will still flow to the remaining bulbs in a string through the nickel wires and bimetallic element. Thus all the bulbs in a string will not necessarily be lit and extinguished simultaneously and an improved glittering effect may result.
While the flasher bulbs shown in FIG. 2 may improve the glittering effect compared with the bulb shown in FIG. 1, certain defects may still exist. Thus, both the bimetallic element B' and the second nickel wire N2' are somewhat delicate and need to be carefully and skillfully spot welded together. This process is such that the bulbs can not readily be mass produced by automatic machinery. Moreover, it is difficult to control the welding process to provide the requisite clearance between the bimetallic element and the nickel wire N1'. The accuracy of the flashing period of the bulb may thus be effected and become irregular.